A typical fuel rail assembly comprises a fuel rail that is securely mounted on the engine to span the engine cylinders and that contains devices that are part of a fuel injection system, such as a pressure regulator and electrically operated fuel injectors. The state of the art has progressed to the point where the fuel rails can be made of a non-metallic material, such as a composite, or plastic. However, metal tubes, typically steel, are still used as inlet and outlet tubes to convey fuel to and from the fuel rail, and also as cross-over tubes between plastic fuel rails that connect opposite cylinder banks in a V-type engine. Each metal tube is connected to the non-metallic fuel rail by means of a joint.
The use of metal tubes for connection to a non-metallic fuel rail is considered to enhance the crashworthiness of a fuel rail assembly in the event of an accident because of the physical characteristics of metal tubing. Ideally, the joint that connects each metal tube to the fuel rail should be equally crashworthy. It should provide a seal that will remain in tact during normal use and during certain crashes to which the automotive vehicle may be subjected. It should also be compatible with mass-production assembly processing techniques.
One known joint for connecting a metal tube to a non-metallic fuel rail comprises a cylindrical metal insert that is disposed at the outer end of a hole in the fuel rail. Assembly of the insert to the fuel rail is accomplished by conventional insert molding techniques. The metal tube that is to be assembled to the fuel rail is inserted into this cylindrical metal insert, and the free distal end of the insert is crimped over a flange on the tube to prevent the tube from coming out of the insert. An O-ring seal between the tube and the insert provides the fluid seal between the two. The O.D. of the insert must itself be sealed to the fuel rail hole, and this is accomplished either by a labyrinth seal or another O-ring. This known joint possesses excellent tube retention, tamper-proofness, and crashworthiness. Unfortunately, the fact that the sealing of the insert's O.D. to the fuel rail hole is not conducive to mass-production fabrication presents a barrier to mass-production fabrication of the joint.
Another known joint for connecting a metal tube to a non-metallic fuel rail comprises an integral circular flange on the fuel rail that surrounds the entrance of the fuel rail hole to which the metal tube is to be joined. The metal tube is inserted directly into that hole, and an O-ring seal between the tube and the hole provides the fluid seal between the two. The radially outer margin of a crimp ring is crimped over the circular fuel rail flange, and the radially inner margin of the crimp ring radially overlaps a flange on the tube to prevent the tube from coming out of the fuel rail hole. While this known joint possesses suitable tube retention, tamper-proofness, and crashworthiness, it too poses a barrier to mass-production processes. This is because the crimping of the crimp ring to the circular fuel rail flange is not conducive to mass-production fabrication and quality control techniques when the fuel rails are fabricated from more brittle non-metallic materials, such as thermoset plastic.
The present invention relates to a new and improved joint for connecting a metal tube to a non-metallic fuel rail which does not pose barriers to mass-production fabrication techniques, such as those that have just been described in the case of the two known joints. Like the first known joint described above, the joint of the present invention retains the advantage of allowing a metallic insert to be insert-molded into the non-metallic fuel rail, but without the level of concern that is necessary for assuring that a fluid-tight seal is provided between the two. This is because the insert-molding step of the present invention inherently creates a satisfactory seal by virtue of the unique construction that results from the unique manner of insert-molding. Like the second known joint described above, the joint of the present invention retains the advantage of allowing the metal tube to seal to a plastic part. The present invention also retains the advantage of allowing the crimp ring to crimped onto metal, as in the first known joint, rather than plastic, as in the second known joint.
The foregoing, along with additional features, advantages, and benefits of the invention, will be seen in the ensuing description and claims which are accompanied by a drawing. The drawing discloses a presently preferred embodiment according to the best mode contemplated at the present time for carrying out the invention.